Thermal reluctance rod thermalretarder for electric water heaters



March 18, 1947. c. M. OSTERHELD 2,417,778

THERMAL REI.|U(.`.`IICE- ROD THERMAL-RETARDER FOR ELECTRIC WATER HEATERSFiled Aug. 27, 1945 2 Sheets-Sheet l /2/ INVENTOR.

CLAR//VOsrm/ffm BY J/vg( March 1s, 1947. 1 M, STERHELD 2,417,778

vTHERMAL RELUC'TANCE ROD THERMAL-RETARDER FOR ELECTRIC WATER HEATERSFiled Aug. 27, 1945 2 Sheets-Sheet 2 Patented Mar. 18, 1947 THERMALRELUCTANCE ROD THERMAL- RETARDER FOR ELECTRIC WATER HEATERS Clark M.Osterheld, Stroughton, Wis., assignor to McGraw Electric Company, Elgin,Ill., a corporation of Delaware Application August 27, 1945, Serial No.612,890

(Cl. B19-39) Claims.

My invention relates to electric heating and particularly to controlsystems for electric heaters of domestic hot water tanks.

An object of my invention is to provide a relatively simple form ofthermal retarder for the single electric heater of a domestic hot watertank that shall be effective to cause energization of the heaterimmediately upon closure of a time controlled switch, or that shallcause energization of such heater with a predetermined time delay periodafter closure of a time-controlled switch.

Other objects of my invention will either. be apparent from adescription of several forms of device embodying my invention or will bepointed out in the course of such description and set forth particularlyin the appended claims.

In the drawings,

Figure 1 is a Vertical sectional view of a domestic hot water tankhaving adapted thereto the elements of my invention shown in diagram aswhen the tank is full of cold water and the time switch is open,

Fig. 2 is a View in diagram ci the thermal elements of Fig. l, exceptthat the position of these elements and the electric contacts are suchas when the upper portion of the tank contains hot water and the lowerportion contains cold water and with the time controlled switch justclosed,

Fig. 3 shows schematically one type of a heat reluctance path,

Fig. 4 is a modification of the device shown in Fig. 3 in which theheating coil may be larger and the heat path longer,

Fig, 5 is a modification o-f Fig. 4 in that the length of the heat flowpath may be varied so as to produce a variable time delay,

Fig. 6 is a front View of the parts shown in Fig. 5,

Fig. 7 is a horizontal sectional View on the line 1 7 0f Fig. 8s

Fig. 8 is a vertical sectional view of a thermal retarder embodying myinvention mounted on the outside of the tank, the retarder comprisingthe elements of Figs. 3, or 4, or 5 and 6, and,

Fig. 9 is a vertical sectional view taken on the line 9 9 of Fig. 8.

Referring iirst of all to Fig. 1 of the drawings, I have thereillustrated a standard domestic hot water tank I I which is providedwith a lower cold water inlet pipe I3 and with an upper hot water outletpipe i5. The tank II is surrounded by a mass I1 of heat insulation whichis held in proper operative position relatively to the tank II by anouter casing I 9.

I provide preferably, but not necessarily, a sin gle electric heater 2I, which if only a single heater is provided is preferably positionedadjacent to the lower end 0f tank I I and which may be positioned in atunnel 23 all in a manner now Wellknown in the art.

I provide a lower thermally-actuable heater control switch 25 which maycomprise a bimetal bar t1, the lower end of which is i'lxedly secured toa xed contact 29 while its upper end is adapted to engage with and bedisengaged from a second fixed contact 3|. While I have illustrated anddescribed a particular form of lower thermally-actuable heater controlswitch 25, I do not desire to be limited thereto since any form ofswitch effective for the same purpose asis switch 25 may be used inplace thereof. The design, construction and adjustment of switch 25 issuch that bimetal bar 21 will be in engagement with fixed contact 3|when it is subject to cold water in the tank and bimetal bar 21 will beout of engagement with fixed contact 3| when subject to hot water in thetank. By cold water I mean Water the temperature of which is on theorder of to say, 130 F. and by hot water I mean water the temperature ofwhich is on the order of F.

I provide an upper thermally-actuable switch comprising a bimetal bar33, the lower end portion of which is adapted to be mounted against aiixed contact 35 subject to the temperature of the water in theintermediate portion of the tank. The upper end portion of bimetal bar33 is mechanically connected with a contact bridging member 31 and whenbimetal bar 33 is subject to cold water in the tank, contact bridgingmember 31 will be in engagement with two Xedly supported contacts 39 and4i. When bimetal bar 33 is subject to hot water in the tank, it willflex so that contact bridging member 31 will be moved out of engagementwith xed contacts 39 and 4 I.

All oi the parts thus far described are already old and well-known inthe art. I provide further a time-controlled switch comprising contactarms 113 and 45 which contact arms are actuated by a time measuringclock or other similar device so that they will be in engagement witheach other during off-peak periods and will be out of engagement witheach other during on-peak periods of each twenty-four-hour day.

I provide a pair of supply circuit conductors 41 and 49 of whichconductor G1 may be connected 'with contact arm 43. Contact arm `l5 isconnected by a conductor 5I to xed contact 39. Fixed contact 4I may beconnected by a conduc,- tor 53 with one terminal of heater 2i, the otherterminal of which may be connected to fixed contact 29. Fixed contact 31is connected by a conductor 55 to the second supply circuit conductor49.

It is evident that if the upper bimetal bar 33 is subject to thetemperature of cold water in the tank and if the Contact bars d3 and l5are moved into engagement with each other as at the start of an off-peakperiod, Contact bridging member 3l will be in engagement with hiredcontacts 39 and 41 whereby enero-ization of heater 21 is efiectedthrough a circuit substantially as follows: from supply circuitconductor through engaged contact arms e5 and 25, through conductor 51,through Contact bridging member 31 and contacts 39 and d1, throughconductor 53, heater 21, through the closed switch 'l5 and from therethrough conductor to the second supply circuit conductor 49. This willmean, therefore, that energization oi heater 2i will be aiectedimmediately upon closure or the time controlled. switch which will occurat the start of an oir-peak period.

Referr g now to f 3 and 9, I have there illustrated in cetail ci 'oun ofdevice embodying 'l retarder struc- "J- a support E:

ral out i le ture is ada' is secured s ner surface has substantialiy thesa ce contour cuter surta-ce or" th il. I may is also made the outer Thesecure supporting block:

bi letal bar 33 is the t surface to carry the member 3i and bim 8 showsthwhen it is subject to so that Contact bridging tact-ing engagementwith "".ie contacts 33 and 5 which be supporte on a block which -shapeand is secured by cr more shortold water in nk 11 member S? is in conoreubsta L .ga-inst member mchine screws.

I provide a support E9 oi heatand electricinsulating material which isof substantially elongated ieri and which may be held against the fronteuri-ace of i5? as by one or more machi I support a second biinetal barl5 at its 'ally f end inst the iront as by aiaachine screw a block 'i'of heatvive'ly high thermal f ng mate i remota-nce. I prov" I member i9which is also secured against the front surface of member as by amachine screw Si. Cn the lower end of member I9 I mount a heating coilthe two terminals of which are adapted to be connected to xed contactsand mounted on member S9. The upper end of r d-lihe member 'i3 is madesubstantially rectangular in section and is provided with an arcuate Thedepression 99 therein.

upper end portion of r nber 'i3 is a counterpart of member is providedwith arcuate depressi n in its lower surface.

I provide a heat insulating cover `91 for member E9 and I may hold thiscover in place by a plurality of machine screws 99.

I provide a means for adjustably varying the thermal reluctance for theheat Iiow path from coil 83 to bimetal bar '13 in the form of a conicalmember 101 which is adapted to be positioned in the opening between thetwo recesses 139 and 9i. Means for varying the thermal reluctance of theheat new path comprises a screwthreaded projection 193 cn the inner endof member 161 which is adapted to t into a screwthreaded opening 105 inthe mid portion of member 59. Means for adjusting the member 13!comprises a stud 191 with a screw driver slot therein and means toindicate the value in convenient terms of the thermal reluctancecomprises a pointer 109 mounted on stud 101 and a dial l El beneath thepointer 199.

I provide further a cover 123 for member 5'1 and. the parts countedthereon. Referring to l, terminal 8l is connected to conductor 51 by aconductor H5 while terminal 85 of the heater S3 is connected by aconductor 111 to the xed contact 29 of the lower thermal switch 25.

:simultaneousl.;7 with the energizaticn of heater 2l upon closure of thetime controlled switch comprising contact arms 43 and 45, an energizingcircuit is closed through heater 83 which will be eiiiective to causegradual temperature rise of the rod "i9, the upper end portion thereof,the member H31, member '1'1 and bimetal bar '13. Bimetal bar i3 will beflexed in a counter-clockwise direction with the result that after apredetermined length of time on the order of four or iive hours, Contactbridging member 93 will be moved into engagement with contacts 39 and41. It is to be understood that the wattage of heater 83 is so selectedthat in combination with the other elements comprising particularly theheat ilow path between coil S3 and bimetal bar will require say four orfive hours until bimetal bar '13 has flexed enough to cause engagementor" contact bridging member 93 with contacts 39 and 4i.

It is evident hat a time delaiT on the order of four to five hours canbe aiected by proper selection of material for the heat ow path betweenth@ coil S3 and the bimetal bar 73.

This construction is shown generally in Fig. 3 of the drawings, while inFig. 4.- of the drawings, I have shown a mo `ication of this idea. Therod 'i9 of high ther ial reluctance has secured thereto at its upper enda -ug 119 the outer end of which is connected to a U-shaped member itialso of high thermal reluctance to the upper end of which is secured thebimetal bar i3. The member Effi will, it is evident, provide a greaterthermal reluctance than that of rod '19 shown in Fig. f3 of thedrawings.

Referring .now to Figs. 5 and 6 of the drawings I have there shown astill further modification, which is also adjustable. The upper end ofrod 'i9 has suitably secured thereagainst member 123 of L--shape whichhas an elongated slot 25 therein. A second bar 52'.' is supported frombar 23 by a cla-mp comprising a bolt 129 having a washer 13 extendingbetween bars 123 and 12'1 and which is adapted to be held by a nut 133having screw-threaded engagement with member 129, an elongated slot 135being provided in member 121. It is thus possible to vary the thermalreluctance of the heat flow path between coil 83 and bimetal bar 'i3 bymoving of member i229 and its operatively associated elements, upwardlyin order to reduce the thermal reluctance and downwardly in order toincrease the thermal reluctance.

Let it now be assumed that at the start of an oit-peak period onlyenough cold water is in the lower part of tant; li to subject the lowerthermally-actuable switch it thereto. The bi metal har will then have'flexed to the position shown in full linea in Fig. 2 and by brokenlines in Fig. 8 of the drawings so that energization of heater Zi willnot occur. Instead energization of heating coil will occur and willcontinue for a length ci time on the order or say, four hours, whenbimetal bar 73 will be caused to flex suciently in a counter-clockwisedirection as shown by broken lines in Figs. 2 and 8, to cause engagementof Contact bridging member 93 with fixed contacts E@ and ill whereby thehereinbefore described energizing circuit through heater 2i will beclosed. Energization ci heater 2l will continue until substantially allof the water in the tanl; is hot when the lower tliernially-actuableswitch will affect deenergization of heater i? i.

Vari is modifications inade in the device o.hodying my invention with:it departing :ii'rorn he spirit and scope thereof and all euchmodifications coming clearly Within the scope ci the appended claimsJshall considered a part ci my invention.

I claim my invention:

ln a thermal retarder heater control switch mit for a domestic hot watertank circuit having an electric heater, the combination with a firsthin-letal bar adapted to loe subject to tank water temperatureintermediate the ends of a tank and a pair of xed contacts in saidcircuit adapted to be engaged by said bimetal bar when subject to coldwater and to be disengaged therefrom when subject to hot water, of asecond bimetal bar adapted to be engaged with and disengaged from saidfixed contacts, a support for one end of Isaid second bimetal har, ofrelatively great length and having appreciable thermal reluctance, andan electric heating coil at the far end of said support adapted to causeflexure of said second bimetal bar int-o engagement with said fixedcontacts with a predetermined time period of delay after energizationthereof.

2. In a thermal retarder heater contro-l switch unit for a domestic hotwater tank circuit hav .ing an electric heater, the combination with arst birnetal bar adapted to be subject to tank water temperatureintermediate the end of a tank and a pair of fixed contacts in saidcircuit adapted to he engaged by said bimetal bar when the latter issubject to cold water, to be disengaged therefrom when the latter issubject to hot water in the tank, or" a second bimetal bar adapted to beengaged with and disengaged from said fixed contacts, a support of rodshape for one end of said Second birnetal bar of relatively great lengthand an electric heating coil at the far end of said support adapted tocause neating and ileXure of said second bimetal bar into engagementwith said xed contacts after a pre- A6 determined time period of delayafter energication thereof.

In a thermal retarder heater control switch unit for a domestic hotwater tank circuit havan electric heater, the combination with abiinetal har adapted to be subject to tank ,ature intermediate the endof a tank ed to be engaged by biinetal bar when the latter subject tocold water, to he disengaged hen the latter is subject to hot Water asecond biinetal bar adapted to engaged with disengaged from said xedtacts, a of rod shape for one end of second bircetal bar or relativelyhigh therreluctance and an electric heatingl coil at ci said supportadapted to cause and iiexure oi said second bimetal into engagement withsaid fixed contacts after a predetermined time period of delay afterenergizaticn or" said heating coil.

a thermal retarder heater control switch for a domestic hot water tank.circuit having electric heater, the combination with a rst biinetal baradapted to be subject to tank water temperature intermediate the end ofa tanir and a pair of iixed contacts in said circuit adapted to beengaged by said bimetal bar when the latter is subject to cold water, tobe disengaged therefrom when the latter is subject to het water thetank, of a second birnetal bar adapted to be engaged with and disengagedfrom said fined contacts, a support or rod shape for one end said secondloinietal bar of relatively h h thermal reluctance and electric heatingc l at rar enel said support adapted to cause slow heating and flexureof said second bibar int-o engagement with said fixed contacts after apredetermined time period ci delay after energization of said heatingcoil, and inanually--actuable means for varying the therreluctance.

5. a thermal retarder heater control switch unit for a domestic hotwater tank circuit having an electric heater. the combination with afirst biinetal bar, a heat-conducting support for said biinetal baradapted to be secured against a tank intermediate the ends thereof tosubject said biinetal to tanlr water temperature and pair of fixedcontacts in said circuit adapted to be engaged immediately by 'saidbimetal bar when the latter is subject to cold water and to bedisengaged therefrom when the latter is subject to hot water in thetank, of a heat-insulating casing supported by said heat-conductingsupport, a support of substantially rod shape in said heat-insulatingcasing, a second biinetal bar secured at one of its ends to one of theends of said support or rod shape, said support of rod shape beingrelatively long and having a relatively large thermal reluctance, aheating coil on the other end or said support of rod shape adapted toraise the temperature or" said second 1oinietal bar and cause it toengage said xed contacts an adjustably pre-determined length of timeafter energizaticn of said heating coil.

CLARK M. OSTERHELD.

